One donated brain can be used for up to 50 different research projects
A charity is urging people to pledge to donate their brains after death to help find a cure for Parkinson's disease.
The Parkinson's Disease Society wants to double the 1,000 or so people on its donor register by the end of the year.
It says brains from people both with and without Parkinson's are needed to boost scientists' understanding.
Newsreader Jeremy Paxman and actress Jane Asher are among stars donating their brains. Parkinson's affects about one in 500 people in the UK.
Ms Asher, who is president of the society and whose brother-in-law has been diagnosed with the disease, said it was essential to secure more donations to the charity's brain bank in London.
There are over 101,000 sufferers in England
More than 10,000 people have the disease in Scotland
Almost 6,000 people suffer from Parkinson's in Wales
Almost 3,500 people are affected in Northern Ireland
Parkinson's occurs as a result of a loss of nerve cells in the brain
There is currently no cure for Parkinson's disease
"Scientific research on brains both with and without Parkinson's is essential," she said.
"It's vital that we secure more potential donors as this will help us move closer to a cure for what can be a debilitating and distressing condition."
Ms Asher assured viewers that any donated brains would be treated with great respect by researchers.
She said: "They are absolutely all used and they are kept frozen, clearly, very, very, very, very, cold, so they last almost indefinitely and every one is used and treated with great respect, I have to say.
"For those who might worry about granny's brain being perhaps not used properly, they are treated with great respect and every brain really does help towards a cure."
Parkinson's is a progressive neurological disorder which can affect movements like walking, talking and writing.
Every year, about 10,000 people are diagnosed with Parkinson's in the UK - one in 20 are under the age of 40.
Famous sufferers of the disease include boxer Muhammad Ali and actor Michael J Fox.
A poll carried out for the charity suggests that, while many people are prepared to donate other organs, there is a reluctance about brain donation.
Of more than 2,000 British adults who were questioned, only 7% were comfortable with the idea of donating their brain. But 63% did not have a problem with heart donation and 65% said they were fine about donating a kidney.
One in three people said they knew someone affected by Parkinson's.
Jane Asher: I will donate my brain
Research using donated brain tissue has already led to major medical breakthroughs in the treatment and understanding of Parkinson's.
The drug levodopa, which has revolutionised the way symptoms of the condition are controlled, was developed following research using donated brains.
The survey suggested that more than a quarter of people were worried that donating their brain would cause distress to their family.
Michael Grycuk's mother Joan had Parkinson's and donated her brain to the register. He said he knew becoming a donor meant a lot to his mother.
"I knew it was something my mother wanted to do. As a result of her generosity and that of many like her, she's provided hope of finding a cure for millions of people around the world currently living with Parkinson's."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.